Answer:
1. physical change
2. Heat flows from the warmer to the cooler object until they are both at the same temperature. The slower molecules gain more thermal energy and collide with other molecules in the cooler object. This process continues until heat energy from the warmer object spreads throughout the cooler object.
3. Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase.
4. "Dry ice" or solid carbon dioxide sublimes
